Rivet

ABSTRACT

The invention relates to a rivet for connecting parts, in particular aircraft components, penetrated by bores, comprising a sleeve part ( 1 ), which has a rivet head ( 11 ) with a cavity running axially and a shank adjoining the rivet head ( 11 ) or is composed of this rivet head ( 11 ), and a rivet mandrel ( 2 ), which has an essentially cylindrical base body ( 26 ) and a widened rivet mandrel head ( 21 ) with respect to the diameter (D) thereof and which penetrates the sleeve part ( 1 ) with its base body ( 26 ) along the cavity. So that a cost-effective connection with improved loadability can be produced between workpieces, even when they have bores of different sizes for the rivet, it is proposed according to the invention that the rivet mandrel ( 2 ) has ribs ( 22 ) running axially on the cylindrical base body ( 26 ).

The invention relates to a rivet for connecting parts, in particular aircraft components, penetrated by bores, comprising a sleeve part, which has a rivet head with a cavity running axially and a shank adjoining the rivet head or is composed of this rivet head, and a rivet mandrel, which has an essentially cylindrical base body and a widened rivet mandrel head with respect to the diameter thereof and which penetrates the sleeve part with its base body along the cavity.

Rivets of this type are produced in large production runs and have a wide application in joining workpieces. In particular when workpieces made of different materials are to be connected and joining techniques such as soldering, welding or adhesive bonding cannot be used, joining using rivets of this type represents a practicable alternative method of connection. The workpieces to be connected are thereby first provided with bores, and the workpieces are placed against one another, ideally with axially aligned orientation of the bore axes. Subsequently, a rivet head of a sleeve part is placed on a borehole of the first workpiece and held there in a fixed manner, and a rivet mandrel penetrating the bores is drawn through the fixed rivet head and a shank optionally adjoining it, until the widened rivet mandrel head thereof comes to bear against the second workpiece or the widened rivet mandrel head has deformed an end-side sleeve part with the formation of a non-positive connection. Non-positive connections of this type are often found, e.g., in aircraft construction, where individual components of different types of materials are combined with one another.

In order to join together different types of workpieces by riveting, it is necessary, as mentioned, to provide them with bores in which there is space for a rivet. In practice, in this context the case often occurs that two bores that are provided to accept a rivet have different bore diameters. If the necessary bores are produced separately in the workpieces, it is difficult to obtain exactly the same bore diameters. But even when workpieces that are to be connected and are made of different types of materials are placed one on top of the other and respectively corresponding bores are produced in one step or through a single drilling operation, the bores thus produced can have different bore diameters due to different material properties. Furthermore, the type of drilling operation can thereby have an impact on the size and shape of corresponding bores, as is known, e.g., for a laser drilling.

If workpieces with different bore diameters are joined together by riveting, the result is that the rivet in the bores cannot bear against all the bore walls or against both workpieces. A connection between the workpieces therefore occurs at least mainly only through a non-positive closure, and one workpiece has a looseness in a plane perpendicular to the bore axes. A loadability of the rivet connection is correspondingly limited.

Attempts have been made according to the prior art to avoid this disadvantage by reaming the necessary bores. However, a reaming operation represents an additional step, which is time-consuming and costly and, in particular in the connection of aircraft components, when thousands of bores are to be reamed on one component, can significantly reduce productivity.

Based on the prior art described above, the object of the invention is to disclose a rivet of the type mentioned at the outset with which a cost-effective connection with improved loadability can be produced between workpieces, even when these workpieces have bores of different sizes for the rivet.

This object is attained through a rivet of the type mentioned at the outset, in which the rivet mandrel has ribs running axially on the cylindrical base body, which ribs are preferably arranged between the rivet mandrel head and the cavity.

A rivet according to the invention in particular has the advantage that when workpieces are connected by drawing the rivet mandrel into or through the rivet head the rivet, due to the ribs provided on the cylindrical base body, bears against both bore walls or workpieces at least in some sections, even with bores of different sizes in the workpieces, and a connection can be easily produced via a non-positive or also via a positive component. Positional inaccuracies caused by an orientation of the bore axes that is not axially aligned can also be offset thereby.

The ribs provided according to the invention are also advantageous from another aspect, because with a placement process by forming material of the workpieces to be connected or of the sleeve part can flow into the free spaces present between the ribs so that drawing in the rivet mandrel compared to a conceivable conical embodiment of a rivet mandrel is facilitated or even made possible at all.

It is thereby advantageous with respect to a uniformly high loadability of a rivet connection when the ribs are arranged in a rotationally symmetrical manner to a longitudinal axis of the rivet mandrel.

It is also favorable in order to utilize or maximize effects of the ribs over the greatest possible length when the ribs adjoin the rivet mandrel head.

As has been shown in tests, it can also be favorable with respect to the largest possible contact surface with an average surface pressure between the rivet mandrel and the shank or the workpieces and consequently a high loadability in terms of strength of a rivet connection, if the ribs at least in some areas have a circular arc-shaped or in particular an acute-angled rib outer contour.

In order to make it possible to draw in the rivet mandrel with a low expenditure of force, the ribs can also be embodied at least in part with wedge surfaces. Alternatively, the ribs can be embodied along their axial extension with essentially the same cross section, which is advantageous with respect to a high surface pressure between ribs and workpieces or shank of the sleeve part. It is also possible for the ribs, seen from the rivet mandrel head in the direction of the rivet head, to first have an area with a constant cross section to which a sloped or wedge-shaped area adjoins. It is thereby possible to draw in the rivet mandrel easily with high surface pressure at the same time.

A rivet mandrel of a rivet according to the invention can be embodied in a hollow manner. However, it is advantageous if the rivet mandrel is embodied in a solid manner, because the rivet mandrel can then better withstand radial forces acting thereon, the rivet connection has a higher rigidity, and a greater tensile force can be exerted on the rivet mandrel while it is being drawn in, without the rivet mandrel being damaged.

The ribs can be applied to the rivet mandrel after manufacture, e.g., by soldering or adhesive bonding or another type of connection. However, every connection point represents a potential weak spot under stress, which is why the rivet mandrel is preferably embodied in a one-piece manner. Rolling or cold working are suitable and simple methods for producing a solid rivet mandrel with ribs running axially.

It has proven useful in a manner to be particularly emphasized if the sleeve part has a shank having a constant outside diameter, the first end of which shank adjoins the cavity of the rivet head and the second end of which shank is in contact with a rivet mandrel head having at least the same outside diameter, the shank being embodied in the direction from the first end to the second end with an expansion area with a constant inside diameter and an adjoining compression area with at least partially increased inside diameter, and the ribs bearing in an area corresponding to the compression area of the shank.

With this variant in a blind-rivet embodiment, an excellent surface pressure can be achieved between the rivet mandrel and the shank as well as between the shank and the workpieces after a placement operation due to the ribs. The ribs make it possible on the one hand for the rivet mandrel to be drawn in with a lower expenditure of force compared to the prior art, because material of the shank can in part flow into free spaces between the ribs and through the deformation a consolidation is achieved which is so high that a highly loadable connection is achieved, but drawing in the rivet mandrel is not made more difficult or impeded. On the other hand, while being drawn in, the ribs at the same time produce an expansion of the shank at least in parts and press it against the bore walls in the workpieces producing a positive connection, so that after the placement operation the shank and the rivet mandrel as well as the shank and the workpieces are firmly connected to one another. A non-positive connection as well as an excellent positive connection is thus given between the rivet mandrel and the shank on the one hand and between the shank and the workpieces on the other hand.

For special purposes, e.g., when the rivet head and the shank are subjected to greatly divergent stresses after the placement of the rivet, it can also be provided for the rivet head and the shank of the sleeve part to be made of different materials. For example, the rivet head and the shank of the sleeve part can be produced separately as single components that together with a rivet mandrel form a kit, which is assembled only upon production of a rivet connection. In this case the single components can be made of different materials that are selected according to the stress to be expected on the single component. It is also possible for the rivet sleeve to be made of one material and to have different properties in the area of the rivet head than in the area of the shank, e.g., after a locally limited heat treatment or a thermomechanical treatment of the rivet head.

When an inner surface of the shank in the compression area is formed according to a surface of the rivet mandrel in the area of the same embodied with ribs, a particularly high surface pressure can be achieved between the shank of the sleeve part and the workpieces as well as between the shank and the rivet mandrel. In this variant of a rivet a non-positive closure as well as a full-surface positive closure is achieved, which leads to highly loadable rivet connections.

The invention is described in more detail below based on exemplary embodiments.

They show:

FIG. 1: A rivet mandrel of a rivet according to the invention;

FIG. 2: A blind rivet before a placement process;

FIG. 3: A blind rivet after a placement process;

FIG. 4: A countersunk-head rivet after a placement process;

FIG. 5 a: A rib located on a base body of a rivet mandrel, which rib is embodied with an essentially identical cross section along its axial extension;

FIG. 5 b: A rib located on a base body of a rivet mandrel, which rib is embodied with a flat wedge surface and an essentially circular arc-shaped rib outer contour;

FIG. 5 c: A rib located on a base body of a rivet mandrel, which rib is embodied with a curved wedge surface and an acute-angled rib outer contour;

FIG. 6: A partial representation of a rivet according to the invention, the sleeve part of which is composed of several component parts;

FIG. 7: Another rivet, the sleeve part of which is composed of several component parts, in a partial representation.

FIG. 1 shows by way of example a rivet mandrel 2 as it is used in a rivet according to the invention. The rivet mandrel 2, which is generally made of a metallic material and is advantageously produced entirely from a high-strength steel alloy in a solid manner, has an essentially cylindrical base body 26 with a longitudinal axis X and a diameter D. Grooves 23 located in the planes perpendicular to the longitudinal axis X and running around this axis can be provided on the base body 26, as shown in diagrammatic form in FIG. 1, via which grooves the rivet mandrel 2 is brought into connection with a rivet head during placement of the rivet or is connected to a rivet head in a positive manner after placement. These grooves 23 are preferably embodied asymmetrically, in order to increase an initial tension. Furthermore, grooves 25 are provided via which the rivet mandrel 2 can be drawn with a placement device. Furthermore, the rivet mandrel 2 has a predetermined breaking point 24, at which the rivet mandrel 2 is designed to break at the end of a placement process or after the production of a rivet connection, so that the end of the rivet mandrel 2 is preferably approximately flush with a rivet head of a rivet. In addition, on one end the rivet mandrel 2 has a rivet mandrel head 21 that is widened with respect to the diameter D of the base body 26, to which rivet mandrel head ribs 22 adjoin. The ribs 22 run axially or parallel to the longitudinal axis X of the rivet mandrel 2 and are arranged in a rotationally symmetrical manner around this longitudinal axis X, a number of the ribs 22 depending on the diameter D of the cylindrical base body 26 and, e.g., with a diameter D of 10 mm, lying between four and ten, so that, on the one hand, the rivet mandrel 2 can be drawn in well but, on the other hand, a high surface pressure is also achieved between the rivet mandrel 2 and a shank or workpieces.

FIG. 2 shows a cross section of a blind rivet according to the invention with a rivet mandrel 2 according to FIG. 1 after insertion in bores of two workpieces 3, 4 to be connected, but before a placement of the rivet. In addition to the rivet mandrel 2 described, the blind rivet comprises a sleeve part 1 with a rivet head 11 and a shank 12, which with one end 121 adjoins the axially extending cavity of the rivet head 11. The shank 12 is embodied with a constant outside diameter. The rivet mandrel head 21 of the rivet mandrel 2 is placed in the area of its second end 122, the rivet mandrel 21 in the mating area on the shank 12 having the same outside diameter as the shank and subsequently being embodied in a tapering manner. This makes it possible to insert the rivet, even if the workpiece 3 is not accessible.

In the interior the sleeve part 1 has an essentially cylindrical cavity in the area of the rivet head 11 and the expansion area A of the shank 12 adjoining it, which cavity accepts the correspondingly dimensioned cylindrical base body 26 of the rivet mandrel 2. In a compression area S adjoining the expansion area A, the shank 12 is embodied with an increased inside diameter compared to the expansion area A, in order to provide space for the ribs 22 of the rivet mandrel 2. The increased inside diameter of the shank 12 is designed such that the ribs 22 bear against the shank 12 inside at some points. The individual parts of the rivet are then no longer disengaged from one another, which facilitates the handling of the rivet during an assembly.

The situation shown in FIG. 2 occurs, as mentioned, before the placement of the rivet, therefore before the rivet mandrel 2 is drawn into the sleeve part 1. If the bores necessary for the rivet in the workpieces 3, 4, have different bore diameters, the shank 12 does not bear against both workpieces 3, 4, but has a free spacing 31 from a workpiece 3 and optionally also from a workpiece 4.

If the rivet mandrel 2 is now drawn into the sleeve part 1 by drawing on grooves 25 while holding the sleeve part on the rivet head 11, the rivet mandrel head 21 placed on the shank 12 causes a compression or deformation of the shank 12 on its second end 122, so that it is folded and a driven head is formed. At the same time, the ribs 22 adjoining the rivet mandrel head 21 penetrate into the area of the shank 12 embodied with smaller inside diameter and produce an expansion of the shank 12 there, so that the looseness 31 present between the shank 12 and workpiece 3 is eliminated. During expansion, if the solid rivet mandrel 2 bears against the shank 12 only in the area of the ribs 22, excess material of the shank 12 can also be forced into free spaces between the ribs 22, so that a good positive closure and a favorable stress distribution in the rivet and the workpieces 3, 4 is achieved. Since the shaft 12 is thin-walled at its end 122, and the rivet mandrel 2 easily slides into the shank 12 due to the ribs 22 shaped in an elongated manner, only slight force is necessary to place the rivet. At the end of the placement process the looseness 31 between the shank 12 and the spacing 6 between the workpieces 3, 4 are finally no longer present and the workpieces 3, 4 are connected to one another in a non-positive and positive manner.

After the placement of the rivet, the base body 26 bears against an inner surface 13 of the rivet head 11 and against the shank 12 essentially over the entire surface. This situation is shown in FIG. 3. In this connection it is favorable, as mentioned, if the grooves 23 are embodied asymmetrically or in a sawtooth manner in cross section, as can be seen from the enlarged section of FIG. 3.

It is obvious to one skilled in the art that a looseness can also be present between the workpiece 4 and the shank 12 before the placement of the rivet. In this case, during placement of the rivet a gap between the shank 12 and the workpiece 3 as well as a gap between the shank 12 and the workpiece 4 are closed due to the deformation of the shank 12. Likewise, the invention covers variants in which the shank 12 is embodied with a constant wall thickness.

Alternatively to the embodiment shown in FIGS. 2 and 3, it is possible with otherwise identical geometric design to apply the ribs to the shank instead of to the rivet mandrel, but this is also associated with higher production costs, since recessing ribs into the shank is more complex than recessing ribs in an outer side of the rivet mandrel.

FIG. 4 shows a rivet according to the invention, in which the sleeve part 1 comprises only a rivet head 12 and no shank is present, after the placement of the rivet. The rivet mandrel 2, which is equipped with a rivet mandrel head 21 embodied as a countersunk head, renders possible a flush installation in the area of a surface of the workpiece 3. With this embodiment variant, the ribs 22 of the rivet mandrel 2 bear directly against the workpieces 3, 4, which are deformed on the bore side through the placement of the rivet, and thus produce a positive closure.

FIGS. 5 a, 5 b and 5 c show possible embodiments of ribs 22, which have proven to be of value in tests. As shown in FIG. 5 a, a rib 22 can be embodied with an essentially identical cross section along its longitudinal extension and an approximately circular arc-shaped rib outer contour 221. During the placement of a rivet according to FIG. 2, the circular arc-shaped front surfaces 222, 223 running parallel to the longitudinal axis X of the rivet mandrel 2 slide along the shank 12 and expand it. Simultaneously, material of the shank 12 can flow into the free spaces present between the ribs 22 and lie against the rib side surfaces 224 there.

In an embodiment further improved over the embodiment according to FIG. 5 a, the ribs 22 according to FIG. 5 b can also be embodied with a sloping front surface 223 that acts as a wedge surface and facilitates a sliding of the rivet mandrel 2 when drawn in.

Finally, FIG. 5 c shows a particularly favorable embodiment of ribs 22. A high surface pressure or optimization of stresses in the rivet and the workpieces 3, 4 with good drawing-in properties of the same are given with this type of shape of ribs 22.

In a further possible embodiment, the ribs 22 can also be graduated and/or embodied with different cross sections.

The ribs 22 are embodied with a length L1 and a width such that when the rivet mandrel 2 is drawn in an expansion of the shank 12 or of the workpieces 3, 4 occurs. If a length of the ribs is at least 25%, preferably more than 40% of the length L of the base body 26 between the rivet mandrel head 21 and a predetermined breaking point 24 and/or the ribs 22 in the rib area B (FIG. 1) cover at least 40%, preferably more than 50% of the outer surface of the base body 26, a particularly effective expansion of the shank 12 and an inflow of material between the ribs 22 that is advantageous for a high surface pressure can be achieved.

Finally, FIGS. 6 and 7 show variants of a rivet according to the invention, which have proven to be advantageous with respect to the closing of an axial gap 6 (FIG. 1). In these variants the sleeve part 1 comprises a shank 12 that is composed of several parts, so that before and/or during a shaping of a driven head an axial force acts on a workpiece 3. For example, with the variant shown in FIG. 6, when the rivet mandrel 2 is drawn in, the upper sleeve 123 is expanded by the ribs 22, the gap between sleeve and top sheet 3 is closed and subsequently the upper sleeve 123 together with the top sheet 3 are carried along and the gap 6 between the sheets is bridged before the upper sleeve 123 as well as the lower sleeve 124 are expanded even more and a loadable positive closure is produced.

In the variant shown in FIG. 7, it is ensured in a similar manner that a force acting axially is exerted on the workpiece 3 even before an expansion of the shank 12 in the direction of the workpieces 3, 4 and an embodiment of a positive closure, so that the gap 6 can be closed. Instead of this type of a multiple-part embodiment of the shank, it can also be embodied in one piece with a predetermined breaking point or one or more predetermined deformation points. 

1. Rivet for connecting parts (3, 4), in particular aircraft components, penetrated by bores, comprising a sleeve part (1), which has a rivet head (11) with a cavity running axially and a shank (12) adjoining the rivet head (11), and a rivet mandrel (2), which has an essentially cylindrical base body (26) and a widened rivet mandrel head (21) with respect to the diameter (D) thereof and which penetrates the sleeve part (1) with its base body (26) along the cavity, characterized in that the rivet mandrel (2) has ribs (22) running axially on the cylindrical base body (26), which ribs are embodied with wedge surfaces (223) directed towards the rivet head (11) and which produce a widening of the shank (12) when the rivet mandrel (2) is drawn in, material of the shank (12) flowing in between the ribs (22).
 2. Rivet for connecting parts (3, 4), in particular aircraft components, penetrated by bores, comprising a sleeve part (1), which is composed of a rivet head (11) with a cavity running axially, and a rivet mandrel (2), which has an essentially cylindrical base body (26) and a widened rivet mandrel head (21) with respect to the diameter (D) thereof, and which penetrates the sleeve part (1) with its base body (26) along the cavity, characterized in that the rivet mandrel (2) has ribs (22) running axially on the cylindrical base body (26), between which ribs material of the parts (3, 4) can flow in when the rivet mandrel (2) is drawn in, the ribs (22) being embodied with wedge surfaces (223) directed towards the rivet head (11).
 3. Rivet according to claim 1, characterized in that the ribs (22) are arranged between the rivet mandrel head (21) and the cavity.
 4. Rivet according to claim 1, characterized in that the base body (26) penetrates the axial cavity bearing against an inner surface (13) of the rivet head (11).
 5. Rivet according to claim 1, characterized in that the ribs (22) are arranged in a rotationally symmetrical manner to a longitudinal axis (X) of the rivet mandrel (2).
 6. Rivet according to claim 1, characterized in that the ribs (22) adjoin the rivet mandrel head (21).
 7. Rivet according to claim 1, characterized in that the ribs (22) at least in some areas have a circular arc-shaped or in particular an acute-angled rib outer contour (221).
 8. Rivet according to claim 1, characterized in that the ribs (22) are embodied along their axial extension with essentially the same cross section.
 9. Rivet according to claim 1, characterized in that the rivet mandrel (2) is embodied in a solid manner.
 10. Rivet according to claim 1, characterized in that the rivet mandrel (2) is produced by rolling or cold working.
 11. Rivet according to claim 1, characterized in that the rivet mandrel (2) is embodied in one piece.
 12. Rivet according to claim 1, characterized in that the sleeve part (1) has a shaft (12) having a constant outside diameter, the first end (121) of which shaft adjoins the cavity of the rivet head (11) and the second end (122) of which shaft is in connection with a rivet mandrel head (21) having at least the same outside diameter, the shaft (12) being embodied in the direction from the first end (121) to the second end (122) with an expansion area (A) with a constant inside diameter and an adjoining compression area (S) with at least partially increased inside diameter, and the ribs (22) bearing in an area corresponding to the compression area (S) of the shank (12).
 13. Rivet according to claim 12, characterized in that the rivet head (11) and the shank (12) of the sleeve part (1) are made of different materials.
 14. Rivet according to claim 12, characterized in that the sleeve part (1) is made of one material and has different properties in the area of the rivet head (11) than in the area of the shank (12).
 15. Rivet according to claim 12, characterized in that an inner surface of the shank (12) in the compression area (S) is shaped according to a surface of the rivet mandrel (2) in the area of the same embodied with ribs (22).
 16. Rivet according to claim 12, characterized in that a length (L1) of the ribs (22) is at least 25%, preferably more than 40% of a length (L) of the base body (26) between the rivet mandrel head (21) and a predetermined breaking point (24) of the base body (26).
 17. Rivet according to claim 12, characterized in that the ribs (22) in the rib area (B) cover at least 40%, preferably more than 50% of the outer surface of the base body (26).
 18. Rivet according to claim 12, characterized in that the sleeve part (1) comprises a shank (12) that is composed of several parts and/or has a predetermined breaking point or a predetermined deformation point, so that an axial force component acts on a part (3) before and/or during a shaping of a driven head. 